Note: Descriptions are shown in the official language in which they were submitted.
O 94/28084 PCTIUS94/06027
SHORT TERM RESIDUAL DUST SUPPRESSION
Backcxround of the Invention-
1. Field of the Inventio:
The present invention relates to short term resid-
ual dust suppression, and more particularly to such sup-
s pressi~on by use of an aqueous mixture of a foaming agent
and a 'wetting agent.
2. Description of the Prior Art
Dust formation from a variety of sources has been
a continuing cause of environmental and health concerns.
Particular attention has been paid to the dust developed
from tlhe handling of coal, but such sources also include,
for example, petroleum coke, recycled glass dust and
bauxite. Thus, while in this specification, reference is
often unade to coal, it should be understood that this
discussion is applicable to numerous other dust sources
as well.
The various industries affected by such dust
formation have engaged in many efforts to avoid or to
alleviate the problem of dust formation that results
_.___ CA 02163972 2004-04-20
- .
2
dtsriag handling, conveya~, transportation and even
storage of cored. sad the other dust scurosa. Tlpiaaily,
sash efforts involve.the use of water incorporated iato a
eh~emiaal dust suppressant applied to the oosl or other .
sou:ns: Ooaweeationsily, 'although the catogories of dust
suppx~easants tiave,overlapped to some is that oer- .:
- taia types of suppressants ~aay be reformulated to bo . '
applied throu5~h a systa~ ~siQ~id for anothor typo, a . .
eappressaat map fbllvinto the categasy of a shoat ~be~
l0 dust auppaeessarit, ; which. ,map be a ~ suppressant oar a .
foau~ supptesssnt,~or a lord term re*idual duet control .
suppressant. short term du*t suppressants function by
Ooatitrp the sous~oe end dust with water. Thus, such enp-
pressants loses their effeOtlveness upon a~taporatioan of
the water. M«reover, their effectiveness generally does
not persist bey~ood o~ t~;tiro impact points that is,
points at whit~.ls dust is Qeherated during handling or
movement of the coal or other eous~oe. 8xaa~plss of wet
and foam.,suppressaats are discussed in U.B. patents ~ .
d,937,~OS.to Dohnar, 4,836,945 to xectner and 4,991,20
to Roe, atsd inz Su~rfaetanta and lnterfaciaZ Phenomsaa. 211
$ditfairi, by Melton J. Rosen, 1~31ep Zrrtersoieroe Publioa-
tiaas (198x): . ~ - . .
Long teas residual dust.suppresssnts vontrol.
dust by maains of they lormation of a polymer or birrdei .
fiLn~ ov!e~c the dust source and thereby persist even after
evaporation o:E water in the suppressant. The present
invention rebates to a new type of short term duet syp_
pressants that may be applied as a wet supp~essaat of as
a foa~a suppressant. .
Wet suppression is based on what is called "wet
technolo~r". This suppression can be as simple ore spray-
ing large $mounts of water on the coal (ar other svuraw).
ns it travels al.onp n conveyor ar drops to a storage pile
or transfer bin. However, although water is an effeotivei
dv*t suppressant, its .use involves a number of drawbacks,.
~'VO 94/28084 216 3 9 7 ~ pCT~S94/06027
3
such as adding weight to the coal or other source (which
can result in higher costs for transporting the source),
development of substantial vapor pressure when the coal
or other source is heated or burned, and the absorption
and thus wasting of substantial energy as the water va-
porizes when the coal or other source is.heated or
burned.
As a result, surfactants or °'wetters" often are
added to the water to reduce the amount of the water
needed for dust suppression. Conventibnal wetters in-
clude nonionic epoxide (e. g., ethylene oxide or propylene
oxide) derived block co-polymers, alcohols of from about
eight to about sixteen carbons'ethoxylated with from
about four to about ten moles of ethylene oxide (wherein
the alcohol may be an aromatic such as alkyl phenol,
preferably nonylphenol, which can be ethoxylated with,
for example, ten moles ethylene oxide), and branched
nonionic surfactants such as branched alpha sulfo ester
salts comprising an acid chain and an alcohol chain of
from about six to about twelve carbons each, and highly
branched alcohol sulfate and alcohol ether sulfate deter-
gents. Generally, the wetter is added to the water in a
weight proportion of from about 0.2 to about 5 parts of
the wetter to about one thousand parts of water. As this
concentration, the wetter acts at the interface between
the coal (or other source) and the water to increase the
affinity of the coal and water, thereby decreasing the
amount of water needed to soak the coal as well as de-
creasing the time required for the water to penetrate the
coal stream.
Typically, such wet technology is employed to
suppress dust generated at transfer points, areas where
the coal falls freely from one point to another (free
falls) such as loading points where the coal is dropped
into a vessel for transportation, impact points where the
coal strikes a surface, and storage areas. The water is
216 3 9 7 2 PCTlUS94/06027
WO 94128084
4
applied at the point of dust generation and is applied to
the air-borne dust as well as to the source of the dust.
If the amount of water added to the coal is sufficiently ,
great, the coal can be prevented from dusting signifi-
cantly on impact. .For such benefits, the water should be ,
added in an amount sufficient to result in a proportion
of one to three parts by weight water per one hundred
parts by weight wetted coal. However, because the sup-
pressant is effective only through one or two impact
points where dust could be generated, repeated applica- .
tions are necessary, thereby increasing the water content
of the wetted coal quickly to seven or eight percent.
Foam suppressants are applied to form a blanket
over the coal or other source to capture and smother
dust. Bubbles in the foam suppressant catch the dust
particles and so the foam suppressant
is effective only until the bubbles break or the layer of
foam becomes discontinuous. The foam suppressant is
formed by addition of a foamer to water. Conventional
foamers include alpha-olefin sulfonates, alkylphenyl
sulfonates with long alkyl chains (e. g., eight to sixteen
carbons) such as sodium lauryl benzene sulfonate, alcohol
sulfates, alcohol ether sulfates, alpha sulfo esters and
mixtures of such compounds. Under standard conditions,
from about one to about twenty parts by weight foamer is
added to about one thousand parts by weight water. The
resulting foam has about five to ten percent of the den-
sity of the water used in wet technology and so much less
water is needed for a foam to provide the same volume of
applied dust suppressant as the wet suppressant. Thus,
the foam suppressant can be added to the coal in a pro-
portion such that the wetted coal contains 0.2 to 0.5 '
parts by weight added water per one hundred parts by
weight wetted coal. However, as with the wet suppres-
sent, the foam suppressant is effective only through one
or two impact points where dust could be generated.
~JVO 94/28084 PCT/US94/06027
2~b3972
Thus, repeated applications are necessary and the water
content of the wetted coal increases quickly to several
percer.~t .
As with wet suppressants, the foam suppressants
5 are employed to suppress dust generated at impact or
transfer points, areas where the coal falls freely from
one point to another (free falls) such as loading points
where the coal is dropped into a vessel for transporta-
tion, impact points where the coal strikes a surface, and
storagfe areas. The foam is applied as'a curtain or bar-
rier t;o capture generated dust. The foam applicator
nozzles are located in such a way that the remaining foam
and the captured dust are deposited back onto the moving
coal stream. This orientation not only prevents dust
from escaping into the environment, but also places at
least a partial blanket of foam onto the deposited coal,
which may prevent dust generation until bubbles are bro-
ken or disrupted by another transfer point. The dust
suppression effects of normal foam does not carry over
from a~ previous application point to further impact zone.
Long term residual dust control suppressants are
used to prevent generation of dust during long term stor-
age or during transportation. Such long term residual
suppressants operate by a mechanism very different from
those of short term residual suppressants to which the
sub~eca invention is directed. In short term residual
(wet or foam) suppression, the water eventually evapo-
rates, rendering the suppressant ineffective in suppress-
ing dust over a long term, such as during several months
of outdoor storage. Thus, long term residual dust sup-
pressa~nts remain active long after the water evaporates.
They ordinarily have some film-forming or tackifying
properties. For example, U.S. patent 4,801,635 to Zinkan
et al. describes a long term residual dust suppressant
that includes an acrylic polymer and U.S. patent
4,169,170 to Doeken describes a long term residual dust
WO 94!28084 216 3 9 7 2 PCTIUS94/06027
6
suppressant that includes an aqueous suspension of as-
phalt emulsion concentrates or black liquor lignin prod-
ucts as a binder material. Conventionally, water is ,
included in a long term residual suppressant'typically
not only to provide some dust control during handling ,
prior to storage, but also to promote even spreading as
the suppressant is applied. Long term residual dust
suppressants often contain wetters or foamers as well to
minimize the amount of water needed to apply the suppres-
sant to the coal and are applied directly to the coal in
what is known as a "main body treatment".
Thus, several problems are associated with conven-
tional wet and foam dust suppression techniques to which
the subject invention is directed. For example, each
technique involves addition of a substantial amount of
water to the coal or other dust source, especially in
view of the repeated applications of water-based suppres-
sant necessary to control dust across several impact or
transfer points. The resulting high water content of the
coal is particularly undesirable in that much dust sup-
pression is performed at fossil fuel power plants. Water
added to the fuel results in a portion of the heat output
of the~coal to be lost to vaporization of the water and
so a loss of effective energy. The vaporization of water
consumes substantial amounts of heat. Therefore, the
addition of such significant amounts of water is particu-
larly troublesome. In addition, the additional water
increases the weight of the coal and so increases ship-
ping costs accordingly.
Because of the substantial disadvantages associat
ed with the addition of such significant amounts of wa
ter, the industry has attempted to minimize the amount of
water employed in wet and foam suppression techniques.
Such attempts typically involve the use of systems for "
application of the suppressant at each dust producing
site instead of a single application that would be in-
2163972
~'VO 94128084 ~ _ PCT/US94/06027
7
tended to last through many transfer points during trans-
port or conveyance of the coal or other dust source.
Becaus:e the suppressant in the multiple application tech-
nique remains effective for only one or two transfer
points, such techniques are expensive; they require cost-
ly ins:tallation~of application equipment at several
transfer points, impact points and loading or "stack-out"
storage sites. In addition, impact sites where dust is
generated often are not accessible to the equipment em-
ployed in conventional application systems. Thus, such
techniques are undesirable.
Summary of the Invention:
Briefly, therefore, the present invention is
directed to a novel aqueous short term residual dust
suppressant. The suppressant comprises from about 50
parts by weight to about 2,000 parts by weight water per
part by weight of a combination of an anionic foamer and
a non~.onic or anionic wetter in a foamer to wetter weight
ratio of from about 1:1 to about 1:20.
The present invention is also directed to a novel
composition of matter useful as a premix for preparation
of an aqueous short term residual dust suppressant. The
composition comprises an anionic foamer and a nonionic or
anionic wetter in a foamer to wetter weight ratio of from
about 1:1 to about 1:20.
The present invention is further directed to a
novel method for short term residual suppression of dust.
The method comprises application of an aqueous short term
residual dust suppressant to a medium prone to liberation
of dust. The dust suppressant comprises from about 50
. parts by weight to about 2,000 parts by weight water per
part by weight of a combination of an anionic foamer and
a nonionic or anionic wetter in a foamer to wetter weight
ratio of from about 1:1 to about 1:20.
Among the several advantages found to be achieved
by the present invention, therefore, may be noted the
WO 94/28084 21 ~ 3 9 7 2 PCT/US94106027
8
provision of a short term residual dust suppressant that
employs less water than previous short term residual dust
suppressants, yet is effective in suppressing dust gener-
ation; the provision of such suppressant that is effec-
tive over multiple~transfer or impact points the provi-
sion of a dry premix to which water may ~e added to form
such suppressants and the provision of .a'rmethod for short
term residual dust suppression that employs less water
than do conventional methods.
Description of the Preferred Embodiments:
In accordance with the present invention, it has
been discovered that a short term dust suppressant that
includes a combination of an anionic foamer and a non-
ionic or anionic wetter in a foamer to wetter weight
ratio of from about 1:1 to about 1:20 in water is very
effective in suppressing dust with surprisingly little
water -- generally less than 0.5 -- often less than 0.2 -
- percent by weight of the wetted dust source such as
coal, and remains effective over several impact points.
This novel aqueous short term dust suppressant, there-
fore, has a residual effect that reduces the number of
re-applications necessary for conventional short term
dust suppressants as the dust source crosses numerous
impact points. This residual effect has been found even
though the suppressant may be free of acrylic polymers or
binders employed in long term residual dust suppressants.
Thus, a short term residual dust suppressant has
been discovered, which enables the suppression of dust
with less water than is employed in conventional process-
es, with fewer applications than required by conventional
processes as the dust source passes across several impact
points, and without the need for acrylic polymers or
binders employed in long term residual dust suppressants.
Surprisingly, therefore, the suppressant utilizes less
water and shows far greater persistence of effectiveness
across impact points than achieved by using either a
21639~~
~VO 94/Z8084 PCT/CTS94/06027
9
wetter or a foamer without the other. For inexpensive
shipping, the foamer and wetter combination may be pre-
pared as a dry or low water pre-mix to-which water can be
added at a later time.
The mechanism involved in achieving such superior
dust suppression with small amounts of water is not known
with certainty. Thus, the present inventor does not wish
to be lbound to any particular theory of operation. How-
ever, at is believed that the dust suppressant forms a
double micelle layer around individual'dust particles, ,
the irvner layer being the wetter (which has a high affin-
ity fo:r solid/liquid interfaces) and the outer layer
being -the foamer (which has a high affinity for water/air
interfaces), with a small amount of water trapped between
the layers. A film, therefore, is formed around the
particle facilitating agglomeration of such coated parti-
cles.
As used herein, the term "foamer" refers to those
surfacitants employed in foam dust suppressants. Such
foamers are generally linear and have a high affinity for
water/air interfaces. Examples of foamers are salts of
alpha-olefin sulfonates, generally linear long chain
(i.e., eight to sixteen carbons) alkylphenyl sulfonates,
generally linear alcohol sulfates, generally linear alco-
hol ether sulfates and generally linear alpha sulfo es-
ters and mixtures of such salts. The generally linear
configuration (i.e., linear with some minor branching
such a.~ a methyl or ethyl group possible, but less desir-
able) permits tight packing of the molecules at the
air/water interface. Foamers useful in the present in-
vention are anionic and water-soluble.
Preferred alpha-olefin sulfonate salts are sodium,
potassj:um, magnesium or ammonium alpha-olefin sulfonates
having from about ten to about fourteen carbons, such as
a product available from Stepan Chemical Company under
the trade designation AS-40, which is in the form of a
PCTIUS94/06027
WO 94/28084
40% by weight aqueous solution of a twelve carbon sodium
alpha-olefin sulfonate.
Preferred long chain alkylphenyl sulfonate salts
have an alkyl chain of about eight to. about sixteen car
s bons, such as sodium lauryl benzene sulfonate.
Preferred alcohol sulfate salts are sodium, potas-
sium, magnesium or ammonium alcohol sulfates having from
about ten to about sixteen carbons formed by sulfating an
alkyl alcohol of from about ten to about sixteen carbons.
10 Preferred alcohol ether sulfate salts may also be
described as salts of alkyl polyalkoxy alcohol sulfates,
and are sodium, potassium, magnesium or ammonium alcohol
ether sulfates having from about ten to about sixteen
carbons, including from one to about six alkoxy -- pref-
erably ethoxy -- units. The alcohol ether sulfate salts
may be prepared by ethoxylating an alcohol of from about
four to about eight carbons with one to about six moles
of ethylene oxide per mole alcohol to produce an ethoxyl-
ated product of the formula RO( CHZCH2 )nH, Wherein R repre-
sents an alkyl group of from about four to about eight
carbons, and then sulfating the ethoxylated product,
followed by salt formation.
Preferred alpha sulfo ester salts are sodium,
potassium, magnesium or ammonium alpha sulfo esters hav-
ing an acid chain of from about two to about sixteen
carbons, including an alcohol chain of up to about six-
teen carbons. In other words, they are the salts of the
esterification product of a two to about sixteen carbon
acid and an alcohol of up to about sixteen carbons.
Preferably, the acid and alcohol are generally straight
chain with little if any branching.
As used herein, the term "wetter" refers to those '
surfactants employed in wet dust suppressants. Such
wetters have a high affinity for water/solid interfaces. '
Wetters are generally, although not necessarily, charac-
terized by their predominantly branched carbon chains
~~6~972
WO 94/28084 PCT/US94/06027
11
(i.e., at least half of the carbons in the carbon chain
are in branches). The carbon chain branches may consti-
tute half of the. hydrophobic carbon chain of the wetter.
Wetters that are not predominently branched are poly-
ethoxylated surfactants that have a large, bulky, hydro-
phylic chain, which allows a relatively~large molecular
"foot~~rint" at the solid liquid interface. The wetters
are w~3ter-soluble and may be an anionic surfactant or a
nonionic surfactant or a mixture of such surfactants.
Examp7Les of wetters that are anionic surfactants are
salts of alpha sulfo esters comprised of an acid chain of
from about six to about twelve carbons and an alcohol
chain of from about six to about twelve carbons and de-
tergents that may be a branched alcohol sulfate or a
branched alcohol ether sulfate. Examples of wetters that
are nonionic surfactants are block copolymers of molecu-
lar weight less than about 600 and derived from ethylene
oxide/propylene oxide or other epoxide, and branched
alcohals of from about eight~to about sixteen carbons
that have been ethoxylated with about four to about ten
moles of ethylene oxide per mole alcohol and mixtures of
such compounds. One such ethoxylated alcohol that is an
ethoxylated alkylphenol is nonylphenol ethoxylated with
ten moles ethylene oxide per mole nonylphenol.
25~ A preferred alpha sulfo ester salt composition is
sold under the trade designation DOSS 70. The composi-
tion comprises seventy percent by weight sodium di-octyl
sulfo-succinate prepared by esterification of 2-ethyl-
hexanol with di-functional sulfonated succinic acid.
The wetter and foamer may be mixed together to
form a pre-mix to which water may be added later to pro-
duce a dust suppressant. The pre-mix may then be shipped
relatively inexpensively in such light weight form and
water may be added after shipping. Alternatively, the
wetter and foamer may be added separately to water. The
wetter and foamer are incorporated into the pre-mix or
WO 94128084 PCTILTS94/06027
2163972
12
final suppressant in a wetter to foamer weight ratio of
from about 1:1 to about 20:1, preferably from about 3:1
to about 10:1. If the wetter and foamer are incorporated
in relative proportions within these.'ranges, the propor-
tion of the wetter.and foamer to water in the suppressant
can vary over a broad range. However, it is preferred
that the weight ratio of the combination of wetter and
foamer to water in the suppressant be from about 1:50 to
about 1:2,000. Thus, if for flowability and handling the
pre-mix contains water in addition to the surfactants in
a weight ratio of, for example, about 4:1 to about 10:1,
the pre-mix would be diluted in water by a factor of,
say, about 25:1 to about 200:1 prior to application to
the dust source. If a dry or low water pre-mix is pre-
pared, water may be added at the site where dust suppres-
sion is to take place.
The suppressant may further includes other ingredi-
ents. For example, foam boosters such as alkyl amine-
oxides, alkynol amides, lignin sulfonates, detergent
range alcohols, ethoxylated alcohols, xanthin gum deriva-
tives and polyethylene glycol may be included. In adds- .
tion, a nonionic alcohol ether solvent such as ethylene
glycol monobutyl ether may be included to prevent gelling
during blending and to stabilize the finished formula-
tion. The suppressant may. also contain a nonionic
hydrotrope such as urea or an anionic hydrotrope such as
sodium xylene sulfonate to prevent gelling during blend-
ing.
The suppressant may be employed as a wet suppres-
sant or as a foam suppressant. If it is to be applied as
a foam suppressant, it can be foamed by conventional
techniques, such as by means of passage of the suppres-
sant through a packed column, a venturi or a static mix-
er. Application as a foam permits greater coverage with '
smaller amounts of water than application as a wet sup-
pressant and ~so foam is preferred.
216397
~VO 94128084 ~ PCT/US94/06027 y
13
As noted above, the preferred weight ratio of
wetter/foamer combination to water in the suppressant is
preferably from about 1:50 to about 1:2,000 (i.e., about.
0.5:1,000 to about 40:1,000). If the suppressant is to
be applied as a wet suppressant, the preferred ratio is
closer to 40:1,000. If the suppressant is to be employed
as a foam suppressant, the preferred ratio is in the
range of about 10:1,000 to about 30:1,000.
The suppressant can be applied to the dust source
by conventional techniques for application of a wet or
foam suppressant, as the case may be. Thus, for example,
the foam suppressant may be applied via nozzles arranged
immediately preceding an impact or transfer point, such
as ~us~t before a free-fall. The nozzles are oriented so
that the foam forms a blanket over the dust source. If
desired, additional nozzles may also be placed under the
dust source for application of the foam suppressant to
form a blanket under the dust source as well as over it.
For example, as coal is conveyed over a ledge for free-
fall into a barge, nozzles may be place above the coal at
the ledge to spray downwardly on the coal, and further
nozzles may be placed under or slightly below the ledge
to spray upwardly or outwardly at the other side of the
moving stream of coal.
The suppressant of this invention is added to the
coal oar other dust source in an amount sufficient to
suppress dust evolution. If the suppressant is added as
a wet suppressant, this amount is generally about 0.05 to
about 2, preferably about 0.2 to about 1, most preferably
about 0.5, percent by weight of the wetted coal or other
source.. If the suppressant is added as a foam suppres-
sant, this amount is generally about 0.05 to about 1,
preferably about 0.05 to about 0.5, most preferably about
0.05 to about 0.2, percent by weight of the wetted coal
or other source. It has been found that these small
amounts are sufficient to maintain dust suppression ef-
CA 02163972 2004-04-20
~14
feGtiveness aoross several impact points even without ~re-
applicatione.
The folleaemples de$cribQ prefer~d emboli.- ,
mmntg of thi ~ ~.nvention. Other embodiments within tt~
S pops of the ala3ms herein will bs appsr~snt to ans , ,
skilled ~,n the ert from consideration of the specifioa~
tiox: or praotlLos of the invention as disclosed hereisi.
=t is intended that the sper.i.fication, togsthss with the
sxs~ntples, ba caonsidereH exea~rlasg only, with the scope
hand spirit of tha invention beir~ indicated by the claisis
. which follow tha e~cs~aplos. In the examples all psx~oent~
epee arc given on a weight Dasis ttnl.ess otherwise ir:di.-
acted.
ALB 1
The following low water pre-mix suppressasit fonau~
lotions were prepared:
Formulation Component Weight ~
A DOSS 7 5TM 12 . 5
48 StrippingsTM 12.5
S.P.A.M.TM 6.0
Water 69.0
B DOSS 75TM 12.5
48 StrippingsTM 12.5
AS-40TM 2.5
Urea 40TM 5.0
Water 67.5
C DOSS 75TM 20.0
48 StrippingsTM 20.0
AS-40TM 10.0
Urea 40TM 5.0
Water 45.0 '
DOSS 70 12.5
ggTM 5 . U
AS-40TM 2 .5
Urea 4 0TM 2 0 . 0
Water 61.5
DOSS 70 20.0
EBTM 10 . 0
AS-40TM 7.5
Urea 40TM 10.0
Water 52.5
' CA 02163972 2004-04-20
Z
F DOSS 70 12.5
EBTM 3 . 5
AS-40TM 2.5
Urea 40TM 35.0
Water 46.5
DOSS 70 17.6
EBTM 8 . 8
AS-40TM 7.5
Urea 40TM 10.0
Water 56.1
H DOSS 70 12.5
EBTM 5 . 0
AS-40TM 2.5
Urea 40TM 25.0
Water 55.0
I DOSS 70 17.6
EBTM Z O . O
AS-40TM 7.5
Urea 40TM 10.0
Water 54.9
DOSS 70 31.5
80 EBTM 12 . 5
AS-40TM 6.0
Urea 40TM 50.0
R DOSS 70 42.0
EBTM 21. 0
AS-40TM 16.0
Urea 40TM 21.0
DOSS 70 38.0
TergitolTM 15-S-7 38.0
AS-40TM 20.0
SXS 40TM 3.0
NeodolTM 23 1.0
CA 02163972 2004-04-20
15A
In these formulations, DOSS 75TM and DOSS 70 repre-
seat a 75% and a 70%, respectively, by weight aqueous
solution of sodium di-octyl sulfo-succinate derived from
esterificatioa of 2-ethyl-hexanol with sulfonated succia-
ic acid (di-fun.ctional). EHTM and 48 StrippingsTM are sol-
vents employed to solvate the wetter, EHTM beiag ethyleae
glycol moaobutyl ether: S.P.A.M.TM is a mixture of AS-40TM
CA 02163972 2004-04-20
16
and lauryl ether sulfate, AS-40TM being a 40% by weight
aqueous soluti~ou of sodium alpha-olefin (C-12) sulfoaate
sold by Stapaa Chemical Company. Urea 40TM is a 40% by
weight aqueous solution of arse. Tergitol"' 15-S-7 is a
noxiionia ~ wetter that is s branched C-15 aloobol with
$lven moles of ethosylati~Ori, sold by union Csrbida. SXSTM
is a hydrotrope which is a 40% by weight aqueous sodium
xylene sulfonate. NeodolTM 23 is a mixture of C-12 and C-
13 alcohol which is a foam or film stabilixsr. Water
Z0 represents added water in gddition to that included in
the DOSS, AS-40TM and Urea 40TM referred to in the chart.
BXANpL$ 2
Water wad m~3.zed with a sample of low water pre-mix
Ci of Esampla 1 in a watex to pre-mix weight ratio of
1S about 80:1. The diluted composition was foamed end ap-
plied by noxsle: at one point at a rate of 2S0 gal.lcas of
water anQ 8.3 gallons of pre-mi~c per hour to coal moving
at 1560 tons par hour. Thus, the resulting added water
ooritent of the wetted coal was O.Q7~ by weight add the
20 pre-mix was add~3d at a rate of 0..005 gaho~ par ton.
The same method was carried out with standard foam ap-
plied at two impact points instead of the single point .
with the foam derived from pre-mix G. The standard foaim
teas added at a rate of 500 gallons of we~t~er and 16.6
25 gallons of star~dlard pre-mid per hour to coal moving at
1560 tons par~hour. Thus, the resulting added water
content of the ra~t~ted.coal was 0.14% by weight and the
~WO 94/28084 216 3 9 7 j2 pCT~S94/06027
17
standard pre-mix was added at a rate of 0.01 gallons per
ton. Measurements of airborne dust were taken at three
pointy along the conveyor for each foam trial and for a
trial. without foam,, with the following average measure-
s ments in milligrams of dust per cubic meter of air at
each measurement point:
Treated with Treated with
Point Untreated Standard Foam Pre-Mix G Foam
.
9.2 2.0 1.3
2' 13.1 . 2.3 1.~ '
3 5.1 2.0 l.I
EXAMPLE 3
'Water was mixed with a sample of low water pre-mix C
of Example 1 in a water to pre-mix weight ratio of about
56:1 .and applied by nozzles at a rate of 450 gallons of
water and 8 gallons of pre-mix per hour to coal moving at
350 tons per hour. Thus, the resulting added water con-
tent of the wetted coal was 0.54 by weight and the pre-
mix was added at a rate of 0.023 gallons per ton. With-
out t~_eatment, the dust level was measured as 80 to 84
seconds of airborne dust observed during charging. Upon
treatnnent, the dust level was measured as 32 to 40 sec-
onds of airborne dust observed during charging.
EXAMPLE 4
Water was mixed with a sample of low water pre-mix G
of Ex~unple 1 in a water to pre-mix weight ratio of about
107:1 and applied by nozzles at a rate of 240 gallons of
water and 2.25 gallons of pre-mix per hour to coal moving
at 875 tons per hour. Thus, the resulting added water
WO 94/28084 ~ ~ ~ PCTIUS94/06027
18
content of the wetted coal was 0.11 by weight and the
pre-mix was added at a rate of 0.003 gallons per ton.
The dust level as measured before and after treatment at '
several points along side the coal conveyor was as fol-
lows (in milligrams per cubic meter of air):
Untreated Treated
2.3 0.5
4.1 0.7
3.2 ~ 1.0
16.6 2.0 '
EXAMPLE 5
Water was mixed with a sample of diluted low water
pre-mix A of Example 1 in a water to pre-mix weight ratio
of about 23:1 and applied by nozzles at a rate of 2040
gallons of water and 90 gallons of pre-mix per hour to
coal moving at 1700 tons per hour. Thus, the resulting
added water content of the wetted coal was 0.50 by
weight and the pre-mix was added at a rate of 0.053 gal-
lons per ton. Effective dust suppression was noted.
In view of the above, it will be seen that the
several advantages of the invention are achieved and
other advantageous results attained.
As various changes could be made in the above
methods and compositions without departing from the scope
of the invention, it is intended that all matter con-
tained in the above description shall be interpreted as
illustrative and not in a limiting sense.
